Radio tuning device



July 28, 1942. BOUCKE 2,291,368

RADIO TUNING DEVICE Filed May 28, 1941 INVENTOR ATTORNEY Patented July 28, 1942 RADIO TUNING DEVICE Heinz Boucke, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation of Germany Application May 28-, 1941, Serial No. 395,587 In Germany January 20, 1940 7 Claims.

Tuning devices are already known in which the movement of the tuning knob is automatically stopped on reaching the proper sharpness of the tuning. For example, electromagnetic devices are employed to this end in which the current is controlled in dependence on the resonance potential of a very selective circuit which is tuned to the intermediate frequency and coupled with the output of the intermediate frequency amplifier.

In accordance with the present invention a tuning device of this type is improved in that between the tuning knob and the part of the tuning device upon which the braking action is exerted, an elastic member is inserted which yields in the direction of rotation of the knob such as, for instance, a flat spring subjected to a torsional stress and which is so dimensioned that only after the tuning knob has been turned through a predetermined angle, which without any braking action would correspond with a change of the adjustment by about 9 kilocycles, will the tuning device overcome the brake force. In this way it is accomplished that on turning the knob the tuning means remains adjusted to the position which tunes in a certain transmitter until the tuning means jumps automatically to the next position for tuning in a neighboring transmitter. This signifies on the one hand an automatic operation of the manual or touch tuning since the tuning performance is converted into a switching performance. Furthermore the advantage is obtained that the disturbance noises lying between stations are not rendered audible.

For an unobjectionable operation of the new tuning device, it must be presupposed (1) that the intermediate frequency circuit furnishing the control current is tuned practically only to the intermediate frequency which corresponds with the carrier frequency (it is only then that precise tuning takes place) (2) that the volume control operates in such a favorable manner that all transmitters are presented with practically identical volume levels. Otherwise the elastic member will, on passing from a powerful transmitter in the direction towards an essentially weaker transmitter, be so adapted that the tuning means jumps over the weak station.

The present invention proposes furthermore to place electric switches between the two parts of the tuning device which are joined by the elastic member. These switches are operated when the two parts are relatively tuned to one another at an angle which when the brake is in the inoperative state, corresponds with a distance of about 9 kilocycles. Through this switch the control potential, or the control current of the brake formed therefrom is rendered ineffective for instance by short circuiting the HF-circuit. This effects a loosening up of the brake whereby the two parts of the tuning device assume again their normal center position. Then a new' braking force will be created which corresponds with the newly set station.

The electric and mechanical time constants of the braking performance are to be so chosen that in the moment in which owing to the traction force of the tensioned spring the tuning means arrives at the new adjustment value (1. e. 9 kilocycles away from the previously set station) or moves past said value, the new retarding performance stops the tuning device. If the control circuit has too much inertia, danger exists that the neighboring stations will be passedover.

In bearing in mind that the tuning operation continues moving under the kinetic energy once received, it is moreover possible to have the said electrical switching-off performance and slowing up performance taking place already at a smaller angular movement than that which corresponds with 9 kilocycles.

Examples of construction of the subject matter of the present invention are shown in the accompanying drawing in which Fig. 1 shows the twopart tuning shaft according to the invention and its association with a circuit of the receiver, Fig. 2 shows the mechanical construction of the tuning shaft and the cooperating switch contacts, Figs. 3, 4 and 5 are modified forms of construction of the two-part tuning shaft, and Fig. 5a is a modified form of the switching device shown in Fig. 5.

Referring to Fig. l the shaft of the tuning knob I is shown divided into two parts 2 and 4 which are joined by means of a fiat spring 3. The shaft 4 carries a disk 5 made from magnetic metal. This disk can be subjected to a braking action produced by the electromagnet 6. This magnet is fastened to the end of an elastic spring 1 and when passed by current it moves forwards towards the disk 5 at a distance of a few millimeters thereby holding said disk.

Figure 2 shows the same arrangement in connection with the described switching device.

In this figure the tuning knob I, disk 5 and magnet 6 are omitted for the sake of clearer illustration. The shaft section 4 has two contacts 8 and 9 mounted thereon, while the appertaining counter contact In is mounted across an interposed insulating piece II to the shaft 2.

The litz wire I2 serves as lead-in for this arrangement. When tuning to a transmitter the contact I is initially in the center position as shown in the figure. If the knob is turned towards the right, while the brake holds the disk with the shaft 4, the contact I0 moves up to the end position shown in dotted lines, at which it touches the contact 9. This results in a switching-off of the control current so that the brake device is put out of operation. To this end, the ends of the winding of the electromagnet 6 can be connected with the contacts 8 and 9 on the one hand and with ID on the other hand, as shown schematically in Fig. 1. Owing to the loosening-up of the brake the disk 5 and shaft 4 move again so that the contact It returns to the center position. The arrangement operates in exactly the same manner when on turning towards the left, the contact I 0 is moved to the contact 8.

In the construction shown in Figure 2, the leadin I2 for the contact II] is in the form of a flexible, thin litz wire. This of course is only possible if one or two revolutions are suflicient to pass with the tuning device from one end to the other one of the scale. If however many revolutions are required it is necessary to provide a transmission across contacts in the manner of a collector.

The tuning device according to the present invention presupposes that on an ranges, or wave ranges a certain angular movement of the tuning k'nob effects approximately the same frequency change. This requirement can be complied with by having in the variable condenser a corresponding plate cut, or by utilizing a cam disk for transmitting rotational forces. Slight frequency deviations are hereby of no consequence since they will be compensated for by the automatic operation.

Figure" 3 shows a further construction of the contact arrangement. In this arrangement the segment I3 takes the place" of the contacts 8 and 9 in Figure 2. The part I5 of the segment consists of conducting material, while the border parts I4 which abut the parts I5 are non-conductive. In this case the switching path is closed in the position of rest and will be briefly opened at a sufficient rotary movement of the knob I towards the right or left. The switching path can be placed into the circuit of the brake magnet,

In Figure 4 there is shown again the tuning knob I, the shaft 2, the elastic part 3 and the shaft 4. The brake device and the wheel for the transmission of the rotary movement are not shown in this figure. The contact I0 is in the form of a pin fastened on an insulator II, The

said pin protrudes into the space formed by contacts 8 and 9 arranged in the manner of a fork. The tubular piece I6 which carries the two contacts 8 and 9' glides on the shaft 4 and by means of the bolt I9 it is prevented from turning on said shaft. The shaft 4 has a threading out thereinto on which the nut I8 can move which is fastened by means of a spring IT to the chassis, or to a part of the tuning device such that the nut can move only parallel to the shaft. The strap 20 maintains the tubular piece IS in connection with the nut I8. Through suitable gearing 2| the tuning device is driven from the shaft part 4.

Figure 5 shows the same arrangement except that it is turned at an angle of 90 with respect to that in Figure 4. It is seen that the contacts 8 and 9 form an angle with one another. When turning the tuning knob several times around, for instance in the direction of a tuning to higher receiving frequencies, the nut I8 moves towards the right and pushes the tubular piece It including the contact fork 8 and 9 likewise towards the right. The further the displacement towards the right is extended the smaller are the turning.

angles of the shaft 2 relative to the shaft 4 which are necessary to release a contact. In order to provide a more favorable matching with the frequency course of the tuning, the lever spring 8 and 9 may also be adapted as shown in Fig. 5a.

It should be further emphasized that the described switching device which at a sufficient relative turning of the wave parts 2 and 4 puts the brake out of operation, also operates already in a purely mechanical manner, for instance without the electric switching-off of the brake. In fact if the contacts or the stop organs I5 in Figure 3 are made so strong that they can withstand the brake force, then when the pin fastened to the wave part 2 reaches the stop organ a further turning of the knob entails a driving of the shaft 4 despite the brake action. This brake action is overcome by the driving force and appears again only at a setting to the neighboring station.

What I claim is:

1. Tuning mechanism for a radio receiver comprising an actuator constituted by two parts and a flexible portion interposed and mechanically interconnected between said two parts, means operative upon adjustment of the receiver to selected station-receiving positions for restraining one of the actuator parts, the flexible portion being such as to permit relative rotation of the second actuator part with respect to the first part and, upon rotation of said second actuator part a predetermined amount, to permit the release of the first actuator part from its restraining means.

2'. Tuning mechanism for a radio receiver comprising a variable tuning reactor adapted upon adjustment to predetermined positions to tune the receiver to successive stations, an actuator for said tuning reactor constituted by two parts and a flexible portion interposed and mechanically interconnected between said two parts, means for restraining one of the actuator parts at the adjusted positions of the tuning reactor, the flexible portion being such as to permit relative rotation of the second actuator part with respect to said one part, said second actuator part adapted to be moved a predetermined amount before the first actuator part is permitted to be released from its restraining means and incidentally permitting the tuning reactor to assume a position for receiving the next successive station.

3. Tuning mechanism for a radio receiver comprising a tuning shaft constituted by two parts and a flexible portion interposed and mechanically interconnected between said two parts,

one of said parts being adapted for connection to the tuning mechanism the other part adapted to be manually controlled, means operative upon adjustment of the receiver to selected station-receiving positions for restraining the said one part, the flexible portion being such as to permit relative rotation of the second shaft part with respect to the first and, upon rotation of said second part a predetermined amount, to

permit the release of the first part from its restraining means.

4. Tuning mechanism for a radio receiver comprising a tuning shaft constituted by two parts and a flexible portion interposed and mechanically interconnected between said two parts, one of said parts being adapted for connection to the tuning mechanism and the other part adapted to be manually controlled, means operative upon adjustment of the receiver to selected station-receiving positions for restraining the said one part, the flexible portion being such as to permit relative rotation of the second shaft part with respect to the first, and means under the control of said other shaft part and upon its rotation through a predetermined angle for making said restraining means ineffective.

5. Tuning mechanism for a radio receiver comprising an actuator constituted by two parts and an interposed flexible portion, an electroresponsive brake mechanism adapted to restrain one of the actuator parts upon adjustment of the receiver to selected station receiving positions, said brake mechanism having a pair of leads connected to the receiver for energizing the same, a pair of spaced contacts carried by said one actuator part and electrically connected to one of the brake mechanism leads, a third contact carried by the other actuator part and electrically connected to the other of said leads, said third contact being normally at a mid-position between said two contacts, and the flexible portion being such as to permit relative rotation of said actuator parts whereby, depending upon the direction of rotation of the second actuator part, its contact coacts with one or the other of the first two contacts to momentarily short-circuit the brake mechanism until the tuning mechanism attains its next adjacent tuning position when the brake mechanism is again operative to lock the tuning mechanism in adjusted position.

6. Tuning mechanism in accordance with the invention defined in claim 5, wherein the first two contacts are spaced apart a distance corresponding substantially to the spacing between adjacent stations as determined by the angular movement of the tuning mechanism.

7. Tuning mechanism for a radio receiver comprising a variable tuning reactor adapted upon adjustment to predetermined positions to tune the receiver to successive stations, a tuning shaft constituted by two parts and an intcrposer flexible portion, one of said parts being adapted for connection to the tuning reactor and the other part adapted to be manually controlled, an electro-responsive brake mechanism adapted to restrain the tuning reactor and its connected actuator part upon adjustment of the receiver to selected station-receiving positions, said brake mechanism having a pair of leads connected to the receiver for energizing the same, a pair of contacts carried by said one actuator part and electrically connected to one of the brake mechanism leads, said contacts being spaced a distance corresponding substantially to the spacing of adjacent stations as determined by the angular movement of the tuning reactor, a third contact carried by the other actuator part and electrically connected to the other of said leads, said third contact being normally at a mid-position between said two contacts, and the flexible portion being such as to permit relative rotation of said actuator parts whereby, depending upon the direction of rotation of the second actuator part, its contact coacts with one or the other of the first two contacts to momentarily short-circuit the brake mechanism until the tuning reactor at tains its next adjacent tuning position when the brake mechanism is again operative to lock the tuning reactor in adjusted position.

HEINZ BOUCKEV 

